/Engine/Source/Runtime/MeshDescription/Public/MeshAttributeArray.h
Example of use: VertexInstanceAttributes().RegisterAttribute( "UV", 8 );
                   . . .
TVertexInstanceAttributeArray& UV0 = VertexInstanceAttributes().GetAttributes( "UV", 0 );
UV0[ VertexInstanceID ] = FVector2f( 1.0f, 1.0f );
template<typename T> TMeshAttributesArray< typename [TMeshAttributesRegisterType](API\Runtime\MeshDescription\TMeshAttributesRegisterType)< T >::RefType > RegisterAttributeInternal ( const [FName](API\Runtime\Core\UObject\FName) AttributeName, const int32 NumberOfChannels, const typename [TMeshAttributesRegisterType](API\Runtime\MeshDescription\TMeshAttributesRegisterType)< T >::RealAttributeType & Default, const EMeshAttributeFlags Flags )